Algorithms

When using the flat terrain version of the model, a release is simulated as a
series of puffs. There are three algorithms used for motion and dispersion of a
release in the atmosphere. The model, using the currently calculated parameters
of a release, internally decides on the use of an algorithm. The algorithms
cover: the jet phase of the release (all densities), the gravitational spread
when a denser-than-air cloud is on the ground, and all other cases (e.g. not
denser-than-air on ground and aloft clouds).

When using the complex terrain version of the model, the motion and dispersion of
the release is determined through the use of fundamental equations of
Navier-Stokes.

The fire algorithms calculate the thermal radiation impact from BLEVEs, Jet Fires
or Flares, and Pool Fires. For Jet and Pool Fires effects such as flame tilt are
calculated.